Facebook shares posted their largest percentage decline in nearly four years, jolting investors who have rallied behind a handful of hot technology firms and raising fresh questions about the resiliency ...

The Dow Jones Industrial Average dropped 330 points today, but the real damage was in the Nasdaq thanks to Facebook (FB), which suffered its largest one-day drop since 2014. •...and explain why Exact Science's naming of Harry Connick Jr. as a spokesperson caused its shares to tumble. The Nasdaq Composite slumped 1.8% to 7344.24.

U.S. stocks joined a broad decline in global equity markets on Monday as traders turned cautious ahead of the Federal Reserve's policy meeting this week and amid continuing concerns about the threat of a global trade war. At the same time, shares of Facebook Inc shed nearly 7 percent after reports that a political consultancy that worked on U.S. President Donald Trump's 2016 campaign gained inappropriate access to data on 50 million of the social network's users.

The Dow Jones Industrial Average was sitting pretty at the end of January. Here's the latest from Barron's reporters... 4:15 p.m. Now that the dust has cleared, the The Dow Jones Industrial Average ended down 335.60 points, or 1.35%, to 24610.91, while the S&P 500 lost 39.09 points, or 1.42%, to 2712.92, and the Nasdaq fell 137.74 points, or 1.84%, to 7344.24. 3:25 p.m. With 35 minutes left in the trading day, the market is off its lows.

U.S. stocks dropped on Monday, with the S&P and Nasdaq suffering their worst day in just over five weeks, as concerns over increased regulation for large tech companies was spearheaded by a plunge in Facebook shares. Facebook shares tumbled 6.8 percent as Chief Executive Mark Zuckerberg faced calls from both U.S. and European lawmakers to explain how a consultancy that worked on President Donald Trump's election campaign gained access to data on 50 million Facebook users. The stock had its worst day since March 2014 and was down 10.8 percent from its closing record hit on Feb. 1, to put the stock squarely in correction territory, a drop of 10 percent from its high.